The present invention is generally related to motor vehicle space frames and more particularly to a modular space frame constructed of individual hydroformed members.
Space frame architecture is increasingly being used in vehicle construction. A space frame is an assembly of individual frame components that are connected at joints to form a cage-like structure on which the other vehicle components are mounted, including the engine, the drive train, the suspension and the hang-on vehicle body parts. Tubular hydroforming potentially offers many advantages in space frame construction because it would enable manufacturers to increase frame stiffness, dimensional stability, fatigue life, and crash worthiness over nonhydroformed space frames while reducing frame mass and cost.
Hydroforming is a metal-forming process in which high pressure fluid is used to outwardly expand a tubular blank into conformity with surfaces of a die cavity of a die assembly to form an individual hydroformed member. Individual blanks can be hydroformed to have a wide range of longitudinal geometries and each hydroformed member can have a cross-sectional configuration that varies continuously along its length. Holes of various sizes and shapes can optionally be punched in the hydroformed member at selected locations along its length during or after the hydroforming process.
Prior art vehicle frames often included frame parts made by forming several structures by stamping and then welding these several individually stamped structures together. Vehicle manufactures can replace this type of frame part with a single hydroformed part, thereby reducing both the number of parts and the number of welds necessary to complete frame construction. Consequently, vehicle weight and assembly costs are reduced. Hydroformed parts also have higher strength, in part because of the plastic deformation of the wall of the blank during the hydroforming process. More particularly, the outward expansion of the wall of the blank during hydroforming caused by the fluid pressure creates a work-hardening effect which uniformly hardens the metal material of the blank. This allows the manufacturer to replace several stamped frame parts with a single stiffer and lighter weight hydroformed part. Hydroforming also produces less waste metal material than stamping.
Thus, tubular hydroforming has many advantages over conventional stamping and welding. The number of frame parts can be reduced and the overall weight of the frame can be reduced through more efficient cross section design and through tailoring of the wall thickness along the length of each hydroformed part while at the same time achieving increased structural strength and frame stiffness. Tooling costs are lowered because fewer parts are required. Stacked tolerances (i.e., dimensional inaccuracies of the frame) are reduced because of the greater dimensional accuracy of each hydroformed part.
It is also advantageous in the automotive industry to be able to use existing equipment to manufacture space frame components. Because most vehicle body designs change each model year, however, it is usually necessary to change the configuration of the vehicle frame to realize a new vehicle body design and this can make frame component manufacturing equipment used for prior vehicle models obsolete.
A modular approach to space frame design can extend the useful life of space frame component manufacturing equipment because this approach allows portions of a space frame to be used for two or more models and yet allows the vehicle body design to be updated. A modular approach to space frame design would be particularly advantageous in space frame design that is constructed of hydroformed members because of the advantages offered by tubular hydroforming. It would thus be desirable in the automotive industry to have a hydroformed modular space frame that can provide easy assembly and allow the reuse of portions of the vehicle space frame among several vehicle models. It is also desirable to manufacture a space frame using as few parts as possible and to reduce stacked tolerances as much as possible.
An aspect of the present invention to meet the needs identified provides a vehicle space frame for constructing a motor vehicle, comprising a body module and a front module. The body module includes a pair of laterally spaced, longitudinally extending main side rail structures and a pair of rearward-most upright structures each being connected to a respective main side rail structure and extending upwardly therefrom to form a pair of rearward-most pillars thereon. The body module further includes a pair of hydroformed upper longitudinal members each being defined by an outwardly deformed tubular metallic wall fixed in a predetermined irregular exterior surface configuration and each including a pillar-forming portion and a longitudinally extending portion. Each pillar-forming portion is connected to a respective main side rail structure and extends upwardly therefrom to form an A pillar and each longitudinally extending portion is connected at an opposite end portion thereof with an associated one of said rearward-most pillars, thereby defining a longitudinal length between the associated A- and rearward-most pillars. A plurality of connecting structures are included in the body module and are constructed and arranged to dispose the main side rail structures, the upper longitudinal members, and the pairs of pillars in laterally spaced fixed relation. The front module includes a pair of front lower side rail structures, a pair of front upper side rail structures and front connecting structure. The front connecting structure is constructed and arranged to connect the front lower side rail structures to one another in laterally spaced relation and the front upper side rail structures to one another in laterally spaced relation. The front module is rigidly fixed to the body module by rigidly interconnecting each front lower side rail structure with a respective main side rail structure and each front upper side rail structure to the pillar-forming portion of a respective hydroformed upper longitudinal member at a position spaced upwardly from the associated main side rail structure.
Other aspects, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.